<footer id="bottom">
  <br>
  <span>
    {{ site.title }} Copyright ©
    {% assign current = "now" | date: "%Y" | plus: 0%}

    {% unless site.footer.since and site.footer.since == current %}
        {{ site.footer.since }}
        -
    {% endunless %}

    {{ current }}
    
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  </span>
</footer>